Flower forcing possibilities in Hemerocallis hybrids

Abstract

Daylilies (Hemerocallis hybrids) are one of the most important ornamental perennial plants nowadays used in gardens and parks. Flower forcing of daylily hybrids in early spring or autumn could broaden their application and marketing possibilities. There is very limited data available on this topic. In our early flower forcing experiment ‘Moonlit Masquerade’, for late flowering ‘Mary Todd’ were used. During the study we have sought answer for the following questions: the amount of growing degree-day required for flower stalk induction and for flowering and whether the day length has an effect on these values or not. In the early flower forcing experiment 4 treatment groups were established: plants of the first treatment group were placed in a moderately heated greenhouse without assimilation lighting. The second treatment group were placed in the same greenhouse but artificial light was used to extend the day length for 15 h. The examination of the third group happened in a plant growth chamber with 15 h day length and a daily average temperature of 20°C was provided for the plants, and there was also a control group in open field environment. For late flowering the bare rooted dormant plants were stored in refrigerator and were planted to open-field in late spring and summer. During the experiments temperature data were logged and plant morphology characteristics were measured in two following year. According to the results it can be stated that the differentiation of inflorescence is not depending on the day length rather on the leaf surface area. Growing degree-day is the main factor which influences the speed of inflorescence development once it has already differentiated, so temperature is the key factor in flower bud opening and it also defines the number of the developing flower buds. The data from late flowering experiment show that bare-rooted daylily plants are suitable for long-term cold storage and this method offers late season flower forcing.